1. Field of the Invention
The present invention relates to a process for screw cutting in a tube or a link made from a composite carbon fiber based material coated with polymerized resin, in which the part of the tube or link comprising the screw thread is inserted in the body of the tube or link and molded on a threaded mandrel.
2. Description of the Prior Art
There exist at the present time tubes and links made from composite materials, for example resin impregnated carbon fibers. The uses thereof are numerous, in particular in the aeronautic field.
These tubes and links are often molded by disposing layers of fibers in a mold, on an inflatable mandrel formed by a bladder connectable to a pressurized fluid source. During curing of the resin, the bladder is inflated which presses the layers of fibers on the internal surface of the mold.
They generally comprise metal end elements bonded or riveted to the tube or assembled by shrink fit therewith.
Attempts have been made to provide tubes and links made from a composite material one of whose ends at least comprises a screw thread.
This result can be attained by molding the end of the tube on a threaded mandrel. Thus the U.S. Pat. No. 2,710,026 describes a process for manufacturing a tube made from a composite material, comprising an end with internal screw-thread, in which a first preform is inserted for receiving the screw thread and partially polymerized in a second preform intended to form the body of the tube and in which the assembly is disposed on a mandrel comprising a threaded portion engaged in the first preform then heated to the desired temperature. But experience shows that this process is not applicable to carbon fiber links or tubes for the fibers of the screw thread portion are not sufficiently compacted and the internal screw thread is not capable of transmitting the forces in the environmental conditions met with in aircraft. Moreover, an inflatable bladder cannot be disposed inside the tube and, after curing, it happens that this latter comprises wrinkled zones.